Centrifuges



Jan. 15, 1963 J. G. GLASSON CENTRIFUGES 3 Sheets-Sheet 2 Filed Aug. 6, 1959 |1| III II INVENTOR. fa 644550 Want/e fin Jan. 15, 1963 J. G. GLASSON 3,073,516

OENTRIFUGES Filed Aug. 6, 1959 3 Sheets$heet 3 IN V EN TOR. J00 G. Gina-saw 3,073,516 CENTREFUGES John G. Glasson, San Rafael, Califi, assignor to Dorr- Oliver Incorporated, Stamford, Comic, a corporation of Delaware Filed Aug. 6, 1959, Ser. No. 832,008 7 Claims. (Cl. 233-28) This invention relates to centrifuges, and more particularly to those which are termed solids-liquid separating centrifuges for the reason that they effect the separation of the solids suspension into overflow and underflow fractions which underflow cannot readily be handled by a liquid-liquid separating type of centrifuge.

Hence, the invention may be said to relate to improvements in a solids separating centrifuge such as exemplifled in the patent to Glasson No. 2,625,321 which has feed inlet means at the top of the bowl, and which differs from the liquid-liquid separating centrifuges in that the solids containing viscous underflow discharges from the bowl through nozzle means preferably of the reaction responsive type located in the outer periphery of the bowl, while the overflow fraction discharges through the neck of the bowl. Another distinction in this type of centrifuge from the liquid-liquid separating type lies in the provision of controlled recirculation of underflow material back through the bottom of the bowl as known for the purpose of controlling the solids concentration in the underflow as well as to prevent plugging by the solids of the discharge nozzle means.

According to the invention, the operation and the effectiveness of such a centrifuge are greatly improved by the provision in one end portion of the bowl, opposite to the overflow end thereof, of novel compartmentation including centrifugal vanes cooperating with feed inlet means as well as with the underflow return. The propeller vanes of a first annular bottom compartment force feed suspension into the bowl, while the propeller vanes of a second compartment adjacent to the first compartment propel returning underflow material into the bowl for discharge in the region of the nozzle means. A controllable supply of wash water may be introduced into the bowl together with the returning underflow with or without underflow material through the last mentioned compartment. As a result of this arrangement, the diameter of the overflow discharge neck is minimized thereby attaining high operational efficiency at a relative minimum power consumption, while precluding any short circuit as between feed inlet and overflow due to their being located at opposite ends of the bowl.

The invention provides that the two compartments cooperate with a central pipe inlet means surrounded by an annular nozzle inlet means. The feed suspension issues from one of these inlet means into one of the compartments, while the return underflow material with or without wash water, or else wash water alone issues from the other one of these inlet means into the other one of these compartments. In one embodiment, underflow return material from the annular nozzle means enters the one compartment which is outwardly located, while feed suspension from a centrally disposed pipe enters the adjoining compartment which is inwardly located.

According to onefeature, provision is made to permit by-passing of thecentral stream of feed suspension through an annular escape passage formed between the terminal rim of a central feed inlet pipe and the inner peripheral edge portion of a common annular dividing wall between the two annular compartments, and the width of this annular passage may be adjustable.

With this by-pass arrangement, sudden surges in the rate of feed supply, or surges in the solids concentration of the feed, or else foam-or-air lock that may occur in one of the compartments may be absorbedand normal operation automatically restored substantially without any ill effects during continued operation. This is so because the excess occurring in the supply is diverted or bypassed through the aforementioned annular escape passage and through the outer vaned compartment into the centrifugal field within the bowl.

More specific features lie in detail arrangements of the inlet means relative to the compartmentation of the bowl.

Other features and advantages will hereinafter appear.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the detailed description of the"- specification as follows:

FIG. 1 is a vertical sectional view of a solids-liquid separating centrifuge howing the novel bowl construction with one embodiment of the compartmentation;

FIG. 2 is an enlarged detail view of the bowl, showing more clearly the compartmentation in the bowl while also illustrating certain features of operation;

FIG. 3 is an enlarged detail showing the improvement; and.

FIG. 4 is a fragmentary View of the bowl illustrating another embodiment of the compartmentation.

The machine herein exemplified to embody the invention is of the solids-liquid separating type wherein a centrifugal bowl it) rotates in a stationary housing 11, the bowl being rotatably suspended by its shaft 8-1 in the usual manner from above the housing. The shaft is connected to the bowl by a hub 10a which has a rim por tion 10b of hollow substantially trunco-conical configura tion marginally connected to the associated narrow end of the bowl and extending inwardly thereof.

The bowl has a constricted top end portion or neck 12 provided with an annular lip 13 from which the overflow fraction may discharge centrifugally across an annular clearance 14 into the overflow compartment 15 constituting the top portion of the housing provided with an overflow outlet connection 16.

The bowl has between its upper and lower trunco-corn'cal end portions an intermediate peripheral portion of relatively large diameter provided with underflow discharge nozzles 17. Such nozzles are spaced along the periphery and are preferably of the reaction responsive type exemplified in the patent to Millard No. 2,695,748. Underflow containing solids from these nozzles discharges across the annular clearance 13 into the surrounding volute portion 19 of the housing intermediate the upper and lower ends thereof, then out through underflow discharge connection 2ft of the housing. An underflow return pipe 21 leads from the volute portion of the housing to the bottom end thereof for the purpose of re-introducing underflow material into the bowl via the lower end thereof and in a manner furthermore to be described.

A discharge valve W may be manipulated to control the rate of underflow recirculation and thus control the underflow discharge concentration in a manner wellknown in the art. A valve W is for admitting controlled amounts of wash water into the return conduit 21. A valve W in the return conduit may be operated to throttle or close the flow through the return connection 21. Thus, the return connection may be closed when it is desired to admit wash water only through valve W into the bowl.

In the example illustrating the invention the bowl has a bottom portion specially constructed to provide a first or inner annular compartment or influent chamber 22 having centrifugal or radially disposed impeller vanes 23, and a second or outer associated annular compartment or influent chamber 24 directly underneath provided with centrifugal or radial impeller vanes 25, which compartments have a common annular dividing wall 26 presenting an inner peripheral edge portion 27. The outer limitation of chamber 24 is represented by an annular wall 100 defining an internal hollow space. These mutually adjoining infiuent chambers 22 and 24 are therefore structurally defined inwardly by the specially shaped rim portion b of the hub, and outwardly by the outer specially shaped annular end wall 10c, and further by the intermediate substantially flat partitioning wall 26.

In conjunction with such compartmentation in the bowl, this invention provides a bottom feed inlet or feed pipe 28 extending through the bottom of the housing and surrounded by annular nozzle member 29A whereby return underflow material passes upwardly into the bottom portion of the bowl, and thus in the same direction as the upwardly directed stream of feed suspension. Preferably annular aspirator nozzle means 29B in turn surround the annular nozzle member 29A whereby any underflow material spilled from volute 19 through space 18 into the lower housing portion is picked up by the aspirating action of the stream of underflow return material from nozzle 29A. With the upper terminal portion of the feed inlet pipe extending upwardly through the central bottom opening of the bowl, the arrangement is such that, normally the feed suspension from the pipe passes on upwardly into the upper or inner vaned annular compartment 22 which communicates with the interior of the bowl, whereas the return underflow material from the nozzle member 29A is deflected radially into the lower or outer vaned compartment 24.

In the present example, the feed inlet pipe has an upper end portion terminating in the region of the lower annular compartment, that is, a distance somewhat below the inner peripheral edge portion 27 of the annular space or passage P. The arrangement in this instance is such that the upward stream of feed suspension from the pipe passes across the annular space and against a deflector cone 30 so it will fan out as indicated by arrows A to be seized by the vanes 23 of the upper annular compartment thus to be forced through communicating passages 23A into the interior of the bowl.

Moreover, the upper terminal portion of the feed inlet pipe is formed with an annular deflector lip 31 which has an overlap O with the inner edge portion of the annular dividing wall (see FIG. 3) so arranged that the upper face F of the lip defines with the inner edge portion of the annular dividing wall the aforementioned passage P. The lower face P of this lip acts to deflect the return underflow material into the lower vaned compartment 24 as indicated by arrows A the return underflow material being seized by the vanes 24 of this compartment causing the material to be centrifugally forced outwardly and upwardly through internal discharge conduits or pipes 32 at high speed into the region of the feed discharge nozzles 17.

Preferably, the centrifugal bowl has an internally disposed hollow sleeve portion 33 surrounding the rotor shaft and rotating with the hub. This hollow hub portion itself is shown to have a slightly tapered outer face provided with a plurality of longitudinal radial ribs 34 over which fit a stack of vertically spaced conical separator discs 35 well-known of themselves.

Vertical perforated feed distributing pipes 36 may be provided to extend through the stack, communicating through the passages 23A with the upper vaned compartment 22.

The annular nozzle member 29A surrounds the feed inlet pipe 28 to constitute therewith an annular passage for the return underflow material. An outer nozzle member herein termed the aspirator nozzle member 2913 is concentric with the first nozzle member constituting therewith a second annular passage around the first mentioned annular passage, through which any leakage of underflow material from the gap 18 is caused to join the upward stream of return material as a result of the aspirator effect produced by these nozzle members.

In operation, the feed suspension is forced upwardly through the distributing pipes 36 into the spaces between the separator discs wherein a well-known manner the light fraction separates from the heavy fraction, which fractions discharge through the neck 12 and through the nozzle 17 of the bowl respectively.

This separation into the two fractions within the centrifugal bowl takes place in a fluid body having a cylindrical inner surface defined by the effective diameter D of the discharge neck 12. Accordingly, the underflow material containing the solids discharges through the nozzles 12 while under the centrifugal pressure of the mass of fluid thus defined. While the diameter of the overflow neck 12 is thus desirably reduced to a minimum dimension, allowing for the annular clearance around the hub portion 33 for overflow discharge, it is noted that the diamter D of the central bottom opening of the lower vaned compartment is somewhat smaller than the neck diameter D and the diameter D; of the central opening in the dividing wall be tween the two vaned compartments may in turn be smaller than the diameter D and that the inner diameter D.,, of the discharge end of the feed pipe 28 may in turn be smaller than the diameter D Let it be assumed first that the feed suspension is continuously supplied at a steady rate of flow and concentration. When the machine is in balanced operation, there results a certain solids concentration in the underflow according to the setting of the discharge valve W with flow material then recirculating at a corresponding rate through the nozzle member 29A into the lower vaned compartment, while the light fraction overflows at a corresponding rate upwardly through the neck 12 of the bowl. If desired, wash water for the underflow solids material may be introduced through valve W into the return conduit 21.

However, it is one of the features of the invention that with the improved construction above described, the machine can absorb such temporarily occurring abnormal conditions as surges in the rate of feed without shortcircuiting the excess into the light fraction discharge of the housing as has occurred where both feed and overflow are located at one end of the bowl. Also, any air lock or foam lock condition that may develop in the upper vaned compartment can be absorbed in the sense that the operation of centrifuge is not interrupted. Both these conditions are relieved by this invention which allows excess amounts of feed to by-pass the upper vaned compartment 22 as is indicated by the flow arrows A shown in dotted lines. That is to say, any excess pressure momentarily caused by foam or air blockage, or else by a surge in the feed, will resolve the congestion by causing the momentary excess to escape through passage P and thus via the lower vaned compartment and through the internal conduits 32 into the interior of the bowl where it is subject to centrifugal separating action even though delivered into the peripheral space surrounding the stack of separator discs. Any such abnormal condition is thus relieved sufliciently until normal operating conditions are re-established. In this way, the feed suspension in any instance, is forced to pass through the centrifugal pressure zone within the bowl to undergo separating treatment, and cannot possibly short-circuit or escape via the light fraction overflow discharge means.

The embodiment of FIG. 4 illustrates the fact that the arrangement can be differently arranged or reversed within the scope of this invention, for example by introducing return material through the central pipe 28' while passing feed through the surrounding annular nozzle 28A. Accordingly, in this embodiment, the feed enters the outer vaned compartment 22 communicating with distributing pipes 36, whereas return material enters the inner compartment 24 communicating with internal discharge conduits 32'. Accordingly, it will be understood that in this embodiment the underfiow discharge have a return connection (not shown) with the pipe 28' including valves corresponding to valves W W and W in FIG. 1, whereas the feed supply connection (not shown) would lead into a space of the housing corresponding to space S in FIG. 1 and thus into the annular space defined by the nozzle 28A.

Another difference between the embodiments of FIG. 4 and FIG. 1 is noted in the fact that the central inlet pipe 28 in FIG. 4 is extended upwardly through the opening in the dividing wall and into the proximity of cooperating auxiliary impeller vanes V provided on the deflector cone 30'. In this way, the suspension issuing from pipe 28' is at once seized by the auxiliary impeller vanes V as well a as by impeller vanes 24a of the inner compartment, with a minimum of kinetic energy required. In this embodiment, the nozzle members 28A and 28B are also extended upwardly through the bottom opening of compartment 22' and thus into the proximity of impeller vanes 22a of the outer compartment 22'.

Furthermore, although it is within the scope of this invention where the bowl rotates about a vertical axis, to provide both feed and return inlets at the top end of the bowl and opposite to the overflow end thereof, in a preferred embodiment such as herein illustrated, the bowl is suspended and driven from above and has the novel compartmentation together with the feed and return inlets provided at the lower end opposite the driven end.

Thus, the compartmentation with feed arrangement and underflow recirculation in the manner of this invention provides improved and highly efficient centrifuge operation wherein power consumption is minimized, shortcircuiting of feed suspension into the overflow discharge is prevented, while at the same time operational disturbances producing air lock, foam lock or undesirable back pressures originated as by feed fluctuations may be overcome and absorbed in the continued operation of the machine. Also, it will be understood that with the present construction, the by-pass relief feature may operate either with or without applying underflow recirculation.

As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the claims.

I claim:

1. In a nozzle type centrifuge with underflow return, the combination which comprises a rotor bowl having truncoconically shaped end portions with their wide ends adjacent to each other to constitute an annular separating chamber; overfiow means at the narrow end of the one of said end portions for centrifugally discharging overflow; discharge nozzles mounted upon the outer periphery of the separating chamber for discharging centrifugally separated underflow material therefrom; a hub having a rim portion marginally connected to and closing the narrow end of the other of said trunco-conical end portions, with a first set of inleading flow passages in the rim portion for introducing feed suspension, and a second set of inleading flow passages in said rim portion for introducing control liquid or suspension, both sets of flow passages disposed around the rotor axis; a group of divergent conduits connected to said second set of inleading passages and having their delivery ends located in said separating chamber in the region of the discharge nozzles for discharging control liquid into said region; a rotor shaft extending from said hub axially through said separating chamber and through the overflow end of the bowl and fastened to said hub; an intermediate annular wall substantially coaxial with the rotor axis located outside the separating chamber and marginally connected to said rim portion and having an intermediate centralinfiuent opening and constituting with said hub and rim portion an inner annular influent chamber communicating with the separating chamber through one of said sets of said inleading passage means and provided with impeller vanes; an outer annular wall substantially coaxial with the rotor axis and having an outer central influent opening and marginally connected to said intermediate annular wall and constituting with said intermediate annular wall an outer annular influent chamber communicating with said separating chamber through the other of said sets of inleading passages and provided with impeller vanes; a first stationary conduit means for supplying feed suspension to the annular infiuent chamber communicating with said first set of inleading passages; and a second stationary conduit means for supplying control liquid or suspension to the annular influen-t chamber, communicating with said second set of inleading flow passages.

2. The arrangement according to claim 1, wherein said rim portion forms a concavity facing outwardly, and said outer Wall forms a concavity facing inwardly and opopsed to said outward facing concavity, and said intermediate annular wall is of substantially fiat configuration.

3. The arrangement according to claim 1, wherein said first and second supply conduit means are substantially concentric with the rotor axis as well as with respect to one another thus constituting a centrally located inlet conduit and an annular inlet conduit surrounding the same, said centrally located inlet conduit being provided with an annular flow diverting lip located in a transverse plane intermediate the plane of said outer central influent opening of said outer annular wall and the plane of said intermediate central influent opening of said intermediate annular wall, said lip having overlapping relationship with the inner edge portion of said intermediate annular wall.

4. The arrangement according to claim 1, wherein said inner influent chamber communicates with the separating chamber through said first set of inleading flow passages, and said outer inlluent chamber communicates with the separating chamber through said divergent conduits.

5. The arrangement according to claim 1, wherein said inner influent chamber communicates with the separating chamber through said divergent conduits, and said outer infiuent chamber communicates with the separating chamber through said first set of inleading flow passages.

6. The arrangement according to claim 1, wherein said rotor shaft is axially secured to said hub by an end screw cap member provided with auxiliary radial impeller vanes cooperating with the vanes in said inner annular influent chamber.

7. The arrangement according to claim 1, with the addition of a housing structure wherein said rotor bowl is mounted for rotation by said shaft, said housing structure having one end portion providing a receiving chamber with outlet means for the overflow, an intermediate portion providing an intermediate receiving chamber with discharge means for the underfiow, and an opposite end portion associated with said concentric inlet conduits, wherein said first and second supply conduit means are substantially concentric with the rotor axis as well as with respect to one another thus constituting a centrally located inlet conduit and an annular inlet conduit surrounding the same, both conduits extending through the respective end portion of the housing, said centrally located conduit means provided with an annular flow diverting lip located in a transverse plane intermediate the plane of the outer central influent opening of said outer annular wall and the plane of the intermediate central influent opening of said intermediate annular wall, and an annular aspirator conduit surrounding said annular inlet conduit and cooperating therewith in efiecting the return of underflow spillage into said separating chamber.

References Cited in the file of this patent UNITED STATES PATENTS Coe Mar. 1, Peltzer et a1. Aug. 22, Andersson June 4, Ayres Nov. 29,

FOREIGN PATENTS Denmark Sept. 12, 1949 

1. IN A NOZZLE TYPE CENTRIFUGE WITH UNDERFLOW RETURN, THE COMBINATION WHICH COMPRISES A ROTOR BOWL HAVING TRUNCO-CONICALLY SHAPED END PORTIONS WITH THEIR WIDE ENDS ADJACENT TO EACH OTHER TO CONSTITUTE AN ANNULAR SEPARATING CHAMBER; OVERFLOW MEANS AT THE NARROW END OF THE ONE OF SAID END PORTIONS FOR CENTRIFUGALLY DISCHARGING OVERFLOW; DISCHARGE NOZZLES MOUNTED UPON THE OUTER PERIPHERY OF THE SEPARATING CHAMBER FOR DISCHARGING CENTRIFUGALLY SEPARATED UNDERFLOW MATERIAL THEREFROM; A HUB HAVING A RIM PORTION MARGINALLY CONNECTED TO AND CLOSING THE NARROW END OF THE OTHER OF SAID TRUNCO-CONICAL END PORTIONS, WITH A FIRST SET OF INLEADING FLOW PASSAGES IN THE RIM PORTION FOR INTRODUCING FEED SUSPENSION, AND A SECOND SET OF INLEADING FLOW PASSAGES IN SAID RIM PORTION FOR INTRODUCING CONTROL LIQUID OR SUSPENSION, BOTH SETS OF FLOW PASSAGES DISPOSED AROUND THE ROTOR AXIS; A GROUP OF DIVERGENT CONDUITS CONNECTED TO SAID SECOND SET OF INLEADING PASSAGES AND HAVING THEIR DELIVERY ENDS LOCATED IN SAID SEPARATING CHAMBER IN THE REGION OF THE DISCHARGE NOZZLES FOR DISCHARGING CONTROL LIQUID INTO SAID REGION; A ROTOR SHAFT EXTENDING FROM SAID HUB AXIALLY THROUGH SAID SEPARATING CHAMBER AND THROUGH THE OVERFLOW END OF THE BOWL AND FASTENED TO SAID HUB; AN INTER- 